Polymer matrix-based sustained-release formulations have gained significant interest in recent years for both parenteral and delivery of small molecules as well as proteins and other biological molecules. These delivery systems offer numerous advantages compared to conventional dosage forms, which include improved efficacy, reduced toxicity, convenience and improved patient compliance. Additionally, colloidal carriers such as microparticles are regarded as providing a promising approach for targeting drugs to specific organs that could permit the sustained release at the target site and reduce potential side effects.
Microparticles of the matrix type that are formed by the process of coacervation are desirable since they permit therapeutic agents to become incorporated into the microparticles under mild conditions. For example, the use of biocompatible and biodegradable anionic and cationic polymers in a coacervation process to form microparticles that incorporate a therapeutic agent has been described by Leong et al. (U.S. Pat. No. 5,759,582) and Walsh et al. (U.S. Pat. No. 6,207,195). Additionally, coacervate microparticles for the delivery of nucleic acids have been described by Roy et al. (U.S. Pat. Nos. 5,972,707 and 6,475,995) and Truong et al. (U.S. Pat. No. 6,410,517).
Coacervate microparticles that can be standardized and employed for the delivery of a variety of therapeutic agents are needed to enhance the efficiency of the formulation process for microparticle sustained release compositions. The invention described herein is directed to address this and other needs.